Summary Assessment and monitoring of exploited fish populations are challenged by costs, logistics and negative impacts on target populations. These factors therefore limit large‐scale effective management strategies. Evidence is growing that the quantity of eDNA may be related not only to species presence/absence, but also to species abundance. In this study, the concentrations of environmental DNA (eDNA) from a highly prized sport fish species, Lake Trout Salvelinus namaycush (Walbaum 1792), were estimated in water samples from 12 natural lakes and compared to abundance and biomass data obtained from standardized gillnet catches as performed routinely for fisheries management purposes. To reduce environmental variability among lakes, all lakes were sampled in spring, between ice melt and water stratification. The eDNA concentration did not vary significantly with water temperature, dissolved oxygen, pH and turbidity, but was significantly positively correlated with relative fish abundance estimated as catch per unit effort (CPUE), whereas the relationship with biomass per unit effort (BPUE) was less pronounced. The value of eDNA to inform about local aquatic species distribution was further supported by the similarity between the spatial heterogeneity of eDNA distribution and spatial variation in CPUE measured by the gillnet method. Synthesis and applications. Large‐scale empirical evidence of the relationship between the eDNA concentration and species abundance allows for the assessment of the potential to integrate eDNA within fisheries management plans. As such, the eDNA quantitative method represents a promising population abundance assessment tool that could significantly reduce the costs associated with sampling and increase the power of detection, the spatial coverage and the frequency of sampling, without any negative impacts on fish populations.

Some studies have suggested that insulin-like growth factor (IGF) pathway is related to premenopausal breast density, one of the strongest known breast cancer risk factors. This study was designed specifically to test the hypothesis that higher levels of IGF-I and lower levels of IGF-binding protein (IGFBP)-3 are associated with high mammographic breast density among premenopausal but not among postmenopausal women. A total of 783 premenopausal and 791 postmenopausal healthy women were recruited during screening mammography examinations. Blood samples were collected at the time of mammography, and plasma IGF-I and IGFBP-3 levels were measured by ELISA. Mammographic breast density was estimated using a computerassisted method. Spearman's partial correlation coefficients (r s ) were used to evaluate the associations. Adjusted mean breast density was assessed by joint levels of IGF-I and IGFBP-3 using generalized linear models. Among premenopausal women, high levels of IGF-I and low levels of IGFBP-3 were independently correlated with high breast density (r s = 0.083; P = 0.021 and r s = À0.124; P = 0.0005, respectively). Correlation of IGF-I with breast density was stronger among women in the lowest tertile of IGFBP-3 than among those in the highest tertile of IGFBP-3 (r s = 0.138; P = 0.027 and r s = À0.039; P = 0.530, respectively). In contrast, the correlation of IGFBP-3 with breast density was stronger among women in the highest tertile of IGF-I than among those in the lowest tertile of IGF-I (r s = À0.150; P = 0.016 and r s = À0.008; P = 0.904, respectively). Women in the combined top tertile of IGF-I and bottom tertile of IGFBP-3 had higher mean breast density than those in the combined bottom tertile of IGF-I and top tertile of IGFBP-3 (53.8% versus 40.9%; P = 0.014). No significant association was observed among postmenopausal women. Our findings confirm that IGF-I and IGFBP-3 are associated with breast density among premenopausal women. They provide additional support for the idea that, among premenopausal women, these growth factors may affect breast cancer risk, at least in part, through their influence on breast tissue morphology as reflected on mammogram.

Despite ongoing efforts to protect species and ecosystems in Cuba, habitat degradation, overuse and introduction of alien species have posed serious challenges to native freshwater fish species. In spite of the accumulated knowledge on the systematics of this freshwater ichthyofauna, recent results suggested that we are far from having a complete picture of the Cuban freshwater fish diversity. It is estimated that 40% of freshwater Cuban fish are endemic; however, this number may be even higher. Partial sequences (652 bp) of the mitochondrial gene COI (cytochrome c oxidase subunit I) were used to barcode 126 individuals, representing 27 taxonomically recognized species in 17 genera and 10 families. Analysis was based on Kimura 2-parameter genetic distances, and for four genera a character-based analysis (population aggregation analysis) was also used. The mean conspecific, congeneric and confamiliar genetic distances were 0.6%, 9.1% and 20.2% respectively. Molecular species identification was in concordance with current taxonomical classification in 96.4% of cases, and based on the neighbour-joining trees, in all but one instance, members of a given genera clustered within the same clade. Within the genus Gambusia, genetic divergence analysis suggests that there may be at least four cryptic species. In contrast, low genetic divergence and a lack of diagnostic sites suggest that Rivulus insulaepinorum may be conspecific with Rivulus cylindraceus. Distance and character-based analysis were completely concordant, suggesting that they complement species identification. Overall, the results evidenced the usefulness of the DNA barcodes for cataloguing Cuban freshwater fish species and for identifying those groups that deserve further taxonomic attention.

Background: A better understanding of factors that affect breast density, one of the strongest breast cancer risk indicators, may provide important clues about breast cancer etiology and prevention. This study evaluates the association of vitamin D and calcium, from food and/or supplements, to breast density in premenopausal and postmenopausal women separately. Methods: A total of 777 premenopausal and 783 postmenopausal women recruited at two radiology clinics in Quebec City, Canada, in 2001 to 2002, completed a food frequency questionnaire to assess vitamin D and calcium. Breast density from screening mammograms was assessed using a computer-assisted method. Associations between vitamin D or calcium and breast density were evaluated using linear regression models. Adjusted means in breast density were assessed according to the combined daily intakes of the two nutrients using generalized linear models.

The analysis of environmental DNA (eDNA) is a powerful tool to increase the efficiency of species detection and monitoring in aquatic ecosystems. Yet, several points remain to be clarified in order to estimate with better precision the distribution and abundance of targeted species, such as the dispersion and dilution of eDNA in large lotic systems. This study aimed to document the dispersion patterns of eDNA in the St. Lawrence River, the largest fluvial system in eastern North America. Caged Brown trout (Salmo trutta) were placed in two different water masses present in this part of the river, the Ottawa River, and water from the outlet of the Laurentian Great Lakes. eDNA detection of the caged fish was performed for two days following cage removal at 53 sampling stations located at 500 upstream, and 10, 100, 500, 1,000, and 5,000 m downstream from the cages. Quantitative PCR analysis using a Brown trout specific assay revealed a positive detection only at downstream stations and up to 5,000 m. To further investigate patterns of dispersion, the relative concentrations of eDNA were predicted using a bidimensional hydrodynamic model, calibrated for downstream advection and lateral mixing of particles (i.e., quantification of 2D dispersion). The detection and the quantities of eDNA obtained by qPCR analyses were compared with the model predictions. Our model which predicts a low lateral mixing and a downstream flow in direct line from the eDNA source best fits the results. We discuss how such studies can improve our capacity to produce more precise estimates of species abundance and distribution in order to better interpret eDNA signals in large lotic systems.